腐殖酸与钙离子共存下ZVI界面沉积过程

为精准分析环境介质在零价铁（ZVI）界面沉积过程和沉积层特性，采用喷涂方法制备ZVI负载芯片，应用耗散式石英晶体微天平（QCMD）研究了腐殖酸（HA）与钙离子（Ca（Ⅱ））在ZVI界面沉积吸附过程的差异，并探讨了Ca（Ⅱ）浓度与HA/Ca（Ⅱ）投加顺序对沉积过程的影响机理.结果表明，在反应体系中先通入HA相较先通入Ca（Ⅱ），ZVI表面形成的沉积层质量更高、沉积层结构更稳定；HA沉积后可促进Ca（Ⅱ）沉积，然而Ca（Ⅱ）先沉积后HA沉积量较少，很大程度上与吸附层外层结构组成差异相关.此外，发现随着Ca（Ⅱ）浓度从10mg/L升高至200mg/L，Ca（Ⅱ）沉积速率加快，界面沉积量增多.QCMD耗散变化研究发现，当Ca（Ⅱ）浓度从10mg/L提高至100mg/L，沉积层耗散变化值（ΔD）逐渐下降，沉积层转变为刚性结构；Ca（Ⅱ）浓度继续加大到200mg/L，ΔD升高趋势，沉积层构象呈现疏松态.应用QCMD可实时监测ZVI钝化层形成的动态变化过程，提供了ZVI界面吸附层变化特征等关键信息.

Deposition process of coexistent humic acid and calcium ion on ZVI interface

In order to gain more insight into deposition behaviors of environmental matrixes on zero-valent iron (ZVI) interfaces as well as the properties of deposited layers, quartz crystal microbalance with dissipation (QCMD) equipped with ZVI-coated sensor prepared by spraying ZVI suspension was applied to investigate the deposition processes of co-present humic acid (HA) and calcium ion (Ca(Ⅱ)) on ZVI interface, including dosing sequence of HA and Ca(Ⅱ), and the effects of Ca(Ⅱ) concentrations. A more stable layer with larger mass was deposited on ZVI surface when HA was initially introduced into the reaction system than that formed when Ca(Ⅱ) was first injected. The deposition of Ca(Ⅱ) was promoted after HA deposition, whereas HA deposition was less significant after Ca(Ⅱ) deposition, which could be attributed to the difference in the structure composition of outer deposition layer. In addition, it was found that both of the deposition rate and layer mass were increased with the increasing Ca(Ⅱ) concentration from 10 to 200mg/L. In particular, the value of change in dissipation (ΔD) gradually decreased when Ca(Ⅱ) concentration increased from 10 to 100mg/L, indicating the more rigid layer formed. However, if continually increasing Ca(Ⅱ) concentration to 200mg/L, ΔD presented an increasing tendency, with an indication of a more loose and softer conformation of the deposition layer. To sum up, it was found that the dynamic and in-situ process of ZVI passivation layer formation could be monitored via QCMD technique, and the characteristics of ZVI adsorption layer could also be provided.